To examine the influence of childhood respiratory infections on adult respiratory health. In 1992-94, community based samples of 20-44 year old people from 48 centers in 22 countries were recruited. Study participants completed questionnaires and underwent lung function testing. On average, 8.9 years later, 28 centres re-investigated their samples using similar methods. 9,175 participated in both studies, of which 10.9% reported serious respiratory infections before 5 years (SRI) and 2.8% reported hospitalisation for lung disease before 2 years (HDL). SRI was associated with current wheeze (OR=1.9; 95% CI=1.7-2.2), asthma (OR=2.5 95% CI 2.2-3.1), and lower FEV1 (89ml 95% CI 54-126), lower FVC (49ml 95% CI 8-90), and FEV1/FVC ratio (-1.2% 95% CI -1.8 to -0.6 ). Childhood respiratory infections were also associated with new asthma (OR 1.5 95% CI 1.03-2.0]), new wheeze (OR=1.5 95% CI 1.0-2.4), and persistent wheeze (OR 2.2 95% CI 1.4-3.6) but not with decline in lung function. Similar findings were observed for HDL. These associations were consistent across centers (p heterogeneity >0.05). SRI was associated with lower FEV1 when excluding ever asthmatics and current wheezers. The impact of early infections was larger in subjects exposed to maternal (p interaction=0.09) or active (p interaction=0.02) smoking. The impact of childhood respiratory infections on respiratory system may not only last into adulthood but also influence development and persistence of adult respiratory morbidity. Eur Respir J. 2008 Nov 14; [Epub ahead of print].